The present invention relates generally to a system for heating railroad switches and rails to keep such components free from ice and snow.
An integral and essential component of railroad system hardware is the switching mechanism employed to shunt rail traffic from one rail line to another. These switches, or switch points, are typically comprised of at least one pair of stationary non-movable stock rails and one or more pairs of movable switch rails and a switch actuator mechanism. The switch may be broken down into two main areas. The switch point area which is near the free end of the movable railing and the switch heel area which is the portion where the switch rails are joined to the stock rails.
Within the railroad community, it is well known that a particular problem encountered during winter months is keeping railroad switches free from ice and snow. If the switches are frozen or jammed such that they may not be moved, they quickly bring the rail system to a stop. Therefore, railroads have been forced to try many methods to free frozen or jammed switches. Traditionally, the railroads employed crews that would use picks and shovels to clear the switches. Another commonly used method was to douse the switch with diesel fuel and ignite the fuel to melt away any ice or snow. Clearly, such methods had substantial drawbacks.
More recently, electrical heating rods and air blowers (both hot and cold) have been used to melt or prevent the accumulation of ice and snow between and around the critical rail sections. The most common type of electrical heater rods presently used are uniform power output constant wattage series cables commonly referred to as tubular heaters, manufactured by Chromalox and others. These heaters are constructed from a series resistance wire encased in a metal tube filled with magnesium oxide dielectric insulation. Generally, they are constructed of a resistance wire having uniform resistance thereby resulting in uniform power output along the entire length of the rod. Such systems often fail due to migration of the resistance wire into contact with the metal tube which causes a short circuit. Additionally, when moisture leaks into the rod, problems arise because the moisture is absorbed by the very hygroscopic magnesium oxide causing either a dielectric failure or steam explosion. Additionally, although such systems are widely used, they are not well suited to sustain the vibration and abuse experienced in the rail environment. Therefore, they fail frequently which can cause disruption in normal rail traffic.
Rod style heaters are usually attached directly to the outside of the stationary (stock) rail. However, since these heaters are relatively long and inflexible, they cannot be bent to fit around the reinforcement braces which hold the stationary rails in place. Therefore, holes must be drilled or slots machined into the braces to allow the heater rods to pass therethrough. The rod style heaters also require a relatively high power output in order to compensate for poor heat transfer between the small diameter rod element and the relatively flat web of the stock rail. This results in large amounts of energy being wasted and extremely high heater temperatures (often the heaters glow red during use). Heaters used under such extreme conditions tend to fail early. Numerous attempts have been made to cover such heater rods with a material that increases the percentage of the energy transferred into the rail versus that lost to the ambient surroundings. For example, attempts have been made to place rod style heaters on the inside of the stock rail in order to have more energy radiate directly into the movable rail. Additionally, housings have been constructed about the heater rods in an attempt to minimize heat loss.
Air blowers operate on the principle that a stream of forced air directed at the gap between the movable point and the stationary rail will blow out any snow that falls into this area. However, in many situations, cold air blowers are inadequate for preventing ice buildup. Hot air blowers direct a stream of heated air into the gap to not only blow out any loose snow but also to melt any ice that may have accumulated to prevent interference with proper switch operation. Hot air blowers can be either electrically heated or gas fired. Unfortunately, the cost of operation is very high because of the large amount of air that must be heated and then exhausted into the environment. Therefore, there is a need for an improved switch point rail heater that consumes a minimum amount of energy while effectively keeping the switch area free from ice and snow.
Similar problems arise when attempting to keep electrified third rails efficiently and reliably de-iced. Therefore, there is a need for cost effective rail heating system for keeping various railroad components free from ice and snow without wasting large amounts of energy.